title: Change in the length of the ulnocarpal ligaments during radiocarpal motion: possible impact on triangular fibrocartilage complex foveal tears.
abstract: OBJECTIVE
  The fovea of the ulnar head is the primary attachment site for both the distal radioulnar and the ulnocarpal ligaments. Thus, both ligaments should be simultaneously affected by the traumatic avulsion of the triangular fibrocartilage complex from its ulnar attachment. Little attention, however, has been directed toward the role of the ulnocarpal ligaments in the mechanics of this type of injury. The purpose of this study was to investigate the changes in length of the ulnocarpal ligaments during various radiocarpal motions and to determine the type of radiocarpal motion that makes the ulnocarpal ligament taut and that could cause foveal avulsion if it were excessive.
  
  
  METHODS
  The 3-dimensional kinematics of the wrist joint were investigated noninvasively using a markerless bone registration technique in vivo. Magnetic resonance images of the wrists of 15 healthy volunteers were acquired in at least 5 positions during each wrist flexion-extension motion, radioulnar deviation, or the so called dart-throwing motion (radial extension-ulnar flexion motion). The 3-dimensional ligament paths of the ulnotriquetral, ulnolunate, ulnocapitate, and palmar radioulnar ligaments were modeled as the shortest paths between the fovea and the insertion point of each ligament. Changes in the 3-dimensional ligament length of each ligament between the neutral position and each wrist position were then calculated.
  
  
  RESULTS
  The lengths of the ulnotriquetral and ulnocapitate ligaments increased the most on wrist radial extension, and the length of the ulnolunate ligament increased the most on wrist extension. The length of the palmar radioulnar ligament changed minimally during any motion.
  
  
  CONCLUSIONS
  The ulnocarpal ligaments are likely to be stretched tensely in wrist radial extension and wrist extension. This study supports the hypothesis that one of the mechanisms responsible for a triangular fibrocartilage complex foveal tear is excessive traction of the ulnocarpal ligament caused by a fall on the outstretched hand.
authors.affiliation: Department of Orthopaedics, Osaka University Graduate School of Medicine, Osaka, Japan. moritomo@ort.med.osaka-u.ac.jp
authors.forename: Hisao
authors.initials: H
authors.lastname: Moritomo
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Murase
authors.forename: Sayuri
authors.initials: S
authors.lastname: Arimitsu
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Oka
authors.forename: Hideki
authors.initials: H
authors.lastname: Yoshikawa
authors.forename: Kazuomi
authors.initials: K
authors.lastname: Sugamoto
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008023:Ligaments, Articular / Q000033:anatomy & histology / Q000502:physiology / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D011884:Radius / Q000502:physiology / Q000503:physiopathology; D016059:Range of Motion, Articular; D012016:Reference Values; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D013180:Sprains and Strains / Q000503:physiopathology; D013314:Stress, Mechanical; D051478:Triangular Fibrocartilage / Q000033:anatomy & histology / Q000502:physiology*; D014457:Ulna / Q000502:physiology / Q000503:physiopathology; D014954:Wrist Injuries / Q000503:physiopathology*; D055815:Young Adult